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|a This paper reports a study of the effect of fluorine implantation on the nickel-induced lateral crystallization of amorphous silicon. To distinguish the effects of the fluorine and the implantation damage, the fluorine implant is either made directly into the a-Si or into the buffer oxide below the a-Si. For a 20 h anneal at 500°C, both types of fluorine implant give a 65% increase in the lateral crystallization width, a five times reduction in the density of nickel silicide precipitates, and an improved grain texture. In contrast, for 20 h anneals at 550 and 600°C, both types of fluorine implant give 29% and 85% reductions in the lateral crystallization width, respectively. The identical results obtained for fluorine implantation into the a-Si and the buffer oxide indicates that the effects observed are due to chemical effects of the fluorine rather than implantation damage in the a-Si. The increased crystallization width at 500°C is explained by the suppression of random crystallization at the bottom a-Si/SiO2 interface. The reduced crystallization widths at 550 and 600°C are attributed to the diffusion and activation of fluorine and the formation of Si-F bonds making the a-Si more resistant to silicide-mediated phase transformation.
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